Insulin-like growth factor (IGF)-II- mediated fibrosis in pathogenic lung conditions.

Sara M Garrett,Carol Feghali-Bostwick,Justin M Thomas,Joseph M Pilewski,Eileen Hsu,Steven O’Reilly

doi:10.1371/journal.pone.0225422

Sara M Garrett, Carol Feghali-Bostwick + Show 4 more

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https://doi.org/10.1371/journal.pone.0225422

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Abstract

Type 2 insulin-like growth factor (IGF-II) levels are increased in fibrosing lung diseases such as idiopathic pulmonary fibrosis (IPF) and scleroderma/systemic sclerosis-associated pulmonary fibrosis (SSc). Our goal was to investigate the contribution of IGF receptors to IGF-II-mediated fibrosis in these diseases and identify other potential mechanisms key to the fibrotic process. Cognate receptor gene and protein expression were analyzed with qRT-PCR and immunoblot in primary fibroblasts derived from lung tissues of normal donors (NL) and patients with IPF or SSc. Compared to NL, steady-state receptor gene expression was decreased in SSc but not in IPF. IGF-II stimulation differentially decreased receptor mRNA and protein levels in NL, IPF, and SSc fibroblasts. Neutralizing antibody, siRNA, and receptor inhibition targeting endogenous IGF-II and its primary receptors, type 1 IGF receptor (IGF1R), IGF2R, and insulin receptor (IR) resulted in loss of the IGF-II response. IGF-II tipped the TIMP:MMP balance, promoting a fibrotic environment both intracellularly and extracellularly. Differentiation of fibroblasts into myofibroblasts by IGF-II was blocked with a TGFβ1 receptor inhibitor. IGF-II also increased TGFβ2 and TGFβ3 expression, with subsequent activation of canonical SMAD2/3 signaling. Therefore, IGF-II promoted fibrosis through IGF1R, IR, and IGF1R/IR, differentiated fibroblasts into myofibroblasts, decreased protease production and extracellular matrix degradation, and stimulated expression of two TGFβ isoforms, suggesting that IGF-II exerts pro-fibrotic effects via multiple mechanisms.

Highlights

Chronic fibrosing lung diseases, such as idiopathic pulmonary fibrosis (IPF) and scleroderma/ systemic sclerosis (SSc)-associated pulmonary fibrosis, are associated with high rates of mortality and morbidity [1,2,3]
Our previous study has shown that Insulin-like growth factor II (IGF-II) transcript and protein levels are significantly increased in lung fibroblasts of patients with SSc compared to normal lung (NL) fibroblasts [12]
We sought to determine the mechanism of insulin-like growth factor (IGF)-II-induced fibrosis, beginning with the role of the IGF-II-responsive receptors, type 1 IGF receptor (IGF1R), type 2 IGF receptor (IGF2R), and insulin receptor (IR)

Summary

Introduction

Chronic fibrosing lung diseases, such as idiopathic pulmonary fibrosis (IPF) and scleroderma/ systemic sclerosis (SSc)-associated pulmonary fibrosis, are associated with high rates of mortality and morbidity [1,2,3]. IPF characteristically affects older males, generally with progressive decline in lung function due to accumulated scarring and fibrosis with a median survival of 2–3 years [2]. Lung disease is the leading cause of death in SSc, which primarily affects women during their child-bearing years and has a median survival of 5–8 years [2].

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